The invention relates to liquid and gaseous fuel burners and more particularly to a compact arrangement of burner components including at least one combustion airflow fan and related conduits capable of efficiently overcoming the high system resistances to combustion gas flow experienced with small boilers, and with long and narrow stacks or exhaust pipes.
Many of the liquid and gaseous fuel burners of the prior art employ radial flow fans which are incapable of overcoming high system resistances to combustion gas flow due to a limitation imposed by the frequency of the alternating current of a stationary power source. A higher fan speed can be achieved through the use of a direct current source as disclosed in German Pat. No. 2,101,462, however, lack of space imposes a limitation on rotor size and even a multi-stage fan cannot overcome system resistances greater than 500 N/qm. Accordingly, these prior art burners are not suitable for use with small boilers having high system resistances, and with long and narrow stacks or exhaust pipes.
German Pat. No. 1,579,792 discloses a vehicle liquid fuel heater equipped with a side channel combustion airflow fan that is capable of trouble-free operation at high system resistances. However, this prior art arrangement requires fan operation at peak level with concomitant high electric power consumption, and is therefore at a disadvantage when applied to a vehicle whose power supply consists of a starter battery allowing for only relatively low electric power consumption. Furthermore excessively high blade speeds are required when operating the side channel fan at peak level, and consequently the burner requires either an auxiliary motor or an elaborate reduction gear for driving low speed accessory apparatus such an an oil pump or a gas compressor.
German Pat. No. 2135093 discloses a multiflow gated side channel airflow fan for use with fuel burner heaters for motor vehicles, wherein the burner output increases with the number of flows while maintaining a sufficiently steep head characteristic to insure pulsation-free burner operation even at relatively low fan speeds. This prior art arrangement is of compact dimension and provides delivery against high system resistance at low electric power consumption, however, it still requires speeds which are too high to allow operation of accessory apparatus without resorting to additional equipment in the form of an auxiliary drive motor or an elaborate reduction gear drive.